I think Grandad1943 should tour the country, addressing his opinions on the management of schools in this virus situation directly to small groups of children, using his habitual phraseology and precision of detail.
They would be 2 metres apart, of course, and while assembling for the talk they would be routed carefully round the school to avoid meeting any other groups coming to the lecture or departing after it. While walking along corridors, they would all wear masks, as they would be closer to one another than 2 metres.An adult would escort them to make sure that the masks stayed on, and no-one was horsing about with excitement at the prospect of being lectured by an outsider adult. All chairs in the lecture room would be disinfected between groups, as would door handles, door edges and frames, and the floor swabbed. The corridor would be swabbed regularly too.
If the children were expected to take notes, or fill in worksheets to show that they had understood and remembered the points made, they would have to bring their own pencils with them, and the worksheets collected (by a pupil wearing a mask?) and returned to him so that he could correct them before the next batch of children arrived.
If anyone seemed to be confused, he would have to see that child individually face-to-face (both wearing masks) and explain again, asking appropriate questions to trigger the child into working out for him/herself why he had advocated certain modes of behaviour. After each individual interview, he would have to wash his hands (yet again) and possibly change the mask.
Meanwhile, the normal teacher of that class is policing the next batch as they assemble for a repeat of the selfsame march to the lecture, each wearing a mask, correctly adjusted, and carrying the right worksheet and their very own pencil (sharpened for the occasion)
Multiply this for each group studying each subject in each year that has returned to school. Multiply again for the number of times the teacher has to explain a detail individually to a child who hasn't quite caught a point, or who was thinking about something else at an important stage of the lesson. Multiply again for random interruptions. In a primary school, the pupils are more likely to stay in one room with the same teacher, but in a secondary school, moement between subjects is more likely.
School is not an office. Children of any age are not adult workers. Having been to school in childhood is not a qualification for knowing all about how schools operate.